The aim of the study is to analyze the effect of ethanol in rich benzene flame, to observe the influence of this oxygenated species and to understand the kinetics of ethanol in the benzene combustion. Two premixed rich benzene/oxygen/argon (11.5% C6H6, 43.2% O2, 45.3% Ar) and benzene/ethanol/oxygen/argon (10.7% C6H6, 2.1% C2H5OH, 43.2% O2, 44.0% Ar) flat flames are stabilized at low pressure (45 mbar) on a burner with the same equivalence ratio of 2.0. Identification and monitoring of signal intensity profiles of species within the flames are carried out using molecular beam mass spectrometry (M.B.M.S.). The substitution of some C6H6 by C2H5OH is responsible for a reduction of the maximum concentrations of main intermediate species such as C2H2, C4H2, C4H4 and C5H6. The UCL mechanism is extended to heavier hydrocarbons, tested against these flames to check its validity and used to underline the effect of ethanol on soot precursors formation. It contains 1028 elementary reactions and 184 chemical species.